Background
Everything was started before BC 8000-9000 by mankind who wanted to get 1-2lt cow`s milk which was produced only for her baby around mesopotamia (South East Turkey and around Syria) and North East Africa (in our century known as Sudan) . After that cattle became a tame animal followed by sheeps and goats and all other animals.

Animal Being Tamed
Civilization tried many different methods to increase daily milk production which was only 1-2kg at that time and to reach 2-3kg weight gain. Some of those methods were pure raising, relative raising, mixing the race, improved race mixed, combination of race mixed and rotated race mixed.

Importance of feeding animals:
Advanced feeding and better caring for animals are essential as well as methods of domestication to increase animal production in any way (milk, meat, strength, wool)

Animals require extra nutrients such as energy, vitamin, mineral to increase 1 kg milk production or 1 kg weight gain or perfect fertility. Animals take most of the nutrients from feed. However, their mineral requirements always higher than feed.

Please see from the above table nutrient and minerals requirements of cows who produce 30-40 lt milk.

Why are trace elements important ?
Trace elements are essential components of an animal’s diet required for a range of metabolic and physiological processes. They are active role in synthesis of hormones and into the structure of some enzymes or check their functioning due to the amount of work in the ration (the animal's daily feed) must be found. Severe deficiency of one element can cause a clinical condition (e.g. Selenium and White muscle disease/muscular dystrophy; Copper and Swayback etc.). More often, the effect of a deficit is insidious, causing ill health and a loss of productivity, without obvious clinical symptoms. Marginal deficiencies affect variable numbers of stock from year-to-year. They are hard to predict and identify, but routine supplementation can be incorporated into the feeding plan. The principle of trace element nutrition should be one of prevention, rather than a response to evidence of a deficiency.

The role of trace elements & vitamins in ruminant feeding.

COBLT (ACo) is required by ruminants for the production of vitamin B12.

A deficiency results in listlessness, loss of appetite, rough coat, scaly skin, reproductive failure and anaemia. Sheep are more sensitive to cobalt deficiency than cattle, whilst young animals are more susceptible than adults.

COPPER (Cu) is a component of red blood cells and is involved in enzyme systems, i.e. haemoglobin synthesis. It is necessary for the pigmentation of wool and hair. Copper is a very important trace element. A deficiency causes retarded growth, loss of appetite, anaemia and scours. Wool may grow straight and straggly; hair tends to fade and is often shed particularly round the eyes. Milk yield is lowered and fertility affected.

A deficiency results in swayback in sheep.

IODINE (I) is incorporated into the hormones produced by the thyroid gland. Thyroid hormones exert control over energy metabolism, physical and mental growth, endocrine glands and the circulatory system.

A deficiency can result in birth of weak, hairless or dead young and infertility. A typical symptom is a swollen neck or goitre.

MANGANESE (Mn) is essential for the correct formation of bone and the development and function of the reproductive system - it is mainly associated with enzyme systems.

A deficiency results in poor growth, leg deformities, poor fertility and abortion.

SELENIUM (Se) promotes growth by improving the correct functioning of muscle and organs such as the liver. Selenium improves fertility and can reduce post-natal losses, particularly in sheep. The anti-oxidant function of selenium means that it is considered closely with Vitamin E.

A deficiency causes muscle weakness, i.e. white muscle disease in lambs, calves and foals and retained placentas in adults

ZINC (Zn) is involved in the growth of body cells, formation of skin, hair, bone and cartilage.

A deficiency results in poor growth, lowered appetite, poor feed conversion and delayed wound healing. In calves skin disorders, stiff gait and the swelling of hocks and knees may result.

VITAMIN A is essential for correct vision and development of bones and mucous membranes. Vitamin A is stored in the liver, which acts as a reserve.

A deficiency results in blindness, infertility, abortion or the production of dead, weak or blind calves. Deficient animals are more easily infected by disease because mucous membranes are weakened allowing bacteria, particularly pneumonia, to enter the tissues.

VITAMIN D3 is a very important vitamin concerned with calcium and phosphorus metabolism in the correct development and maintenance of bones and teeth. Its requirement is greatest during pregnancy and lactation.

A deficiency can cause bone weakness (rickets) and poor growth rates. It is also believed to be involved in milk fever.

VITAMIN E has a broad spectrum of activity including fat metabolism, reproduction and muscle function. It is essential for conversion of carotenes to Vitamin A.

A deficiency results in muscle weakness affecting reproduction, heart, liver, lungs, brain and renal activities.

How can trace element availability/deficiency be determined ?

The best indication of an animal’s trace element status can be obtained through a combination of pasture sampling and/or blood/tissue samples of affected animals.

Pasture samples: The following table summarises what would be considered low and high values for trace elements in forages. Pasture samples should be soil free.

It should be noted that the adequacy of pasture copper also depends on the levels of molybdenum and sulphur in the pasture.  Any test should include all three elements.

Blood and tissue samples:  This is the most common way for the veterinary profession to identify a deficiency. However, interpretation of the results can be a problem because of the continuous nature of the values.  There is no distinct ‘cut-off’ where a decline in productivity or clinical symptoms will occur.  This explains why a range of values is often reported in the literature.  Researchers in New Zealand and Australia responded by undertaking dose response trials with large numbers of animals, which predict the likely benefit from supplementation.  Where possible, these values have been adopted in Table 2.

Table 2.  Summary of the biochemical data used as guidelines to diagnose trace element deficiencies.

Refs: Clark et al  1989; Langlands et al  1989; Grace and Clark 1991; and Whitaker 1999

The following summarises some of the constraints and common problems encountered with the various diagnostic methods: -

Cobalt: While the cobalt status can be assessed by measuring the serum Vitamin B12 (pmol/l) levels, the test is of limited diagnostic value for adult cattle. A better alternative is to determine the cobalt content of the pasture or diet. If this is below 0.11 mg/kg DM (0.11 ppm on a dry basis), deficiency in lambs and calves is likely. If it is below 0.07 mg/kg DM for extended periods then deficiency is inevitable.

Copper: Direct measurement of the copper levels in serum or plasma is an accurate assessment (µmol/l). However, because the levels can rapidly change, its diagnostic value can be limited. Copper levels in the liver provide a better assessment of the overall copper status in the previous few weeks - while biopsies are possible, realistically liver samples are only obtained at slaughter.

Iodine: In field conditions, assessing the thyroid hormones thyroxine (T4) and tri-iodothyronine (T3) is of little diagnostic value in adult cattle, unless a representative sample of animals has been taken, and the results assessed together with dietary information, season and even stage of lactation. The thyroxine (T4) values presented in table 2 are based on the assertion by Whitaker (1999) that the use of 50 nmol/l by Veterinary Investigation centres as the lower limit could be the cause of misdiagnosis of iodine deficiency. Plasma inorganic iodine (PII mg/l) is now accepted as a sensitive indicator of iodine intake during the previous 2-3 days, although data is still limited on how values correlate with clinical findings. Accurate diagnosis of iodine deficiency can be achieved post-partum by examining the thyroid dissected out of a fresh calf carcass. The weight of a clean thyroid should normally be less than 0.0375 % of the calf body weight (15g for a 40 kg calf). A similar relationship exists for sheep where thyroid gland: body weight ratios greater than 0.46 g/kg is indicative of goitre associated with severe iodine deficiency, but not necessarily with sub-clinical deficiency.

Manganese: Blood manganese values vary widely between individuals and the diagnostic value is limited.

Selenium: While blood selenium levels can be measured, a more common method of assessing selenium status is to measure the enzyme Glutathione Peroxidase (GHSPx), which is found in the red blood cells (hence PCV). It is important to note that the test should be undertaken at 370C - failure to do so is often a cause of error. Given the lifespan of red blood cells, it takes a few weeks for GHSPx to respond to selenium supplementation.

Zinc: Zinc in blood serum or plasma is a widely used indicator of zinc status but there are factors other than diet that affect the concentration. For example, stress and a difficult calving can depress the value.
 

What factors affect trace element content and availability ? 

Forage trace element content and availability is affected by soil type; antagonistic trace elements; fertiliser practices; irrigation; water logging etc.

Antagonists: Trace element availability varies because of interactions between elements with similar physical or chemical properties which act as antagonists.  For example, zinc and iron compete with copper for sites of transfer across the intestinal tract. 

In the ruminant a secondary deficiency in copper is often accentuated by the presence of molybdenum which reacts with sulphur in the rumen to form a thiomolybdate complex.  The thiomolybdate complex in turn reacts with copper to reduce its availability for absorption.  Unattached thiomolybdate is also absorbed and either reacts with copper in tissues or interferes with the activity of copper metalloenzymes. 

Goitrogens in clovers and brassicas can be considered antagonists.  They affect the uptake and metabolism of iodine in the thyroid. 

Irrigation and water logging:  Copper deficiency is often seasonal.  Water logging increases the molybdenum availability and reduces that of copper. 

Fertiliser practices:  Fertilizers can alter the concentrations of trace elements on pastures.  Liming raises the pH, increases molybdenum and selenium but decreases the content of cobalt, manganese, iron and zinc in pasture.  The use of nitrogen, phosphorous and potassium fertilisers to increase pasture dry matter (DM) production does not appear to have any consistent effects in the plant uptake of trace elements. Changes in the grass-legume ratio will alter trace element content as clovers normally contain higher levels of trace elements. 

Basal Rock type:  As a general rule, rocks that are rapidly weathered (basic basalt types) give rise to soils with adequate trace element levels.  In contrast, acidic slowly weathered granitic types give rise to soils low in trace elements, particularly selenium, cobalt and iodine. However, rock type is not the best guide and local experience is necessary.  It is better to rely on animal and pasture samples.

How can calculate  animal’s trace element daily requirements ?

When we calculate daily tace element requirements we should take into account these parameters.

1)      Animals’ life part : This requirements are needed for carrying on the life.               (-Growing of body  -Protecting body temperature )

2)      Yield of livestock : average of daily, monthly, yearly.

a)  Milk yield

b)  Meat yield

c)  Wool yield

d)  yield offspring

e)   Extra phisical activity : oxes, bulls etc

3)  contaminant of animals : feces, urine,  sweats, teardrop etc…

 Contents of 1 kg milk :   

 Milk composition :

What are an animal’s trace element requirements ?

To some extent, this will depend on the level of antagonists present. For example, in the case of copper, normally, 5-6 mg/kg DM in the diet is sufficient for grazing sheep and cattle.  When antagonists like molybdenum reduce copper availability, 10 mg/kg DM copper in the herbage may not be adequate.  Table 3 summarises the animals requirements.  A simple method of calculating an animal’s total trace element requirement is to assume the daily DM intake of cattle is around 2.5% of liveweight (LW).  A 500 kg cow would therefore eat 12.5 kg DM per day.  With sheep, 2.8% of liveweight (LW*0.028) would be acceptable guide to intake.

Summary of the dietary trace element requirements for ruminants.

Do animals get their mineral requirements from different type of feed?

Answer to that question is YES If they are the first domesticated animals by mankind. However,  current vitamins and minerals requirement of animals are very high. Therefore,  animals feed can not meet current vitamins and minerals requirement of animals by itself.

Daily amounts (mg) of trace elements required and the amounts provided by 12.5 kg dry matter of marginal herbage (for a 500kg cow).